What are the practical uses of expensive, feature rich DMMs?

[kcbrown]

Would the Mooshimeter work?   https://moosh.im/mooshimeter/

600V Cat III rating (no idea if the rating is bunk or not, but at least it gives an idea of the voltages it can measure), bluetooth interface.

Might be worth a look.

Of course, if the requirement is to be able to measure voltages in the thousands range, then that's basically out.

[Fungus]

Would the Mooshimeter work?   https://moosh.im/mooshimeter/

No, because he requires 1GOhm impedance on voltage measurements.

Finding a 300V meter isn't difficult, it's the special requirements.

[Kleinstein]

There are essentially 2 options:
1) a 1 GOhm's (or similar) divider, with all it's trouble - usually the cheaper way, especially with more channels, but limited accuracy
2) a electrometer type instrument: here a actively driven voltage source is used to compensate for the input voltage. This is usually more accurate and input impedance is often >10 GOhms (but usually not accurately known). However this is the more expensive way and combining with a scanner can be tricky.

So it depends on the accuracy needed. If the source impedance is known one might be able to correct for the loading effect.

[b_force]

I don't understand why someone would want to buy a $500 multimeter. What can you do with something like this that you can't do with a multimeter from walmart?

A multimeter is only as good as what it is used for.
Second to that is that people just like to buy (show off) proper stuff because it feels right for them.
In essence that's just marketing doing its job.

You need to pick a meter for what you're going to use it for.
So if you don't care about a billion extra digits, than simply stick to a cheap multimeter.
There is one thing about trust though. With that I mean trust in your measurements.
But to be very honest, most meters nowadays are performing all within specs for a couple of years.

What is important for me personally, is that the meter is sturdy enough.
I had some meters in the past, but the switch broke every time (of course in the most important moments), which was so frustrating.
For that reason I bought a very decent Brymen.
Also I always like to have that extra digit simply to see how certain voltages are behaving.
For most circuits it's not needed though.

[Fungus]

There is one thing about trust though. With that I mean trust in your measurements.

I'd argue that owning two (or more) cheap meters gives more trust than a single expensive meter.

If you own a single meter how do you know it's working? You need at least a voltage/resistance/current reference apart from the meter.

What is important for me personally, is that the meter is sturdy enough.
I had some meters in the past, but the switch broke every time (of course in the most important moments), which was so frustrating.
For that reason I bought a very decent Brymen.

Owning 2+ cheap meters also solves that problem better than owning a single expensive meter.

[Fungus]

There are essentially 2 options:
1) a 1 GOhm's (or similar) divider, with all it's trouble - usually the cheaper way, especially with more channels, but limited accuracy
2) a electrometer type instrument: here a actively driven voltage source is used to compensate for the input voltage. This is usually more accurate and input impedance is often >10 GOhms (but usually not accurately known). However this is the more expensive way and combining with a scanner can be tricky.

I was just reading the manual fro one of those old push-button 1970s Flukes. Some of them have a 10 GOhm impedance mode for measuring voltage.

[alm]

I'd argue that owning two (or more) cheap meters gives more trust than a single expensive meter.

If they are regularly compared and come from different sources, then maybe. But I would still argue that in regular use the chance of a cheap meter going wrong is higher than the root of the chance of an expensive meter going wrong (so both cheap meters may well die before the expensive meter dies). See attached data on 250 calibrations of an HP/Agilent 34401A in the 10 V range. Of the 250 calibrations over a period of 8 years (calibration interval 1-2 years), none of the calibrated meters were found to be out of spec when they came in. This would give me a pretty good confidence that the 34401A is unlikely to drift out of its fairly tight specs at 10 V. If you look at all ranges, 12 out of 250 where out of tolerance on any range. Often at ranges were a cheap meter will not even measure, like 100 V AC at 20 kHz. What kind of data do you have on the cheap meters that two of them would beat that? Especially taking into account the tolerances of the 34401A compared to a cheap meter?

Keep in mind that a more expensive meter will often have tighter specs, so while that 0.025% accurate meter could have drifted out of spec, it may very well still be closer than that 1% accurate meter. It is actually quite rare to find an old Fluke meter that is out of spec if not grossly abused. And if it is out of spec, it is often obvious. No such history is available on most cheap meters.

If you want to be absolutely sure about accuracy, send the meter out for regular calibration. If the meter was in spec before and after your measurement, then you can be pretty sure your measurement is accurate. This is much more effective than throwing more meters with unknown history at the problem.

I was just reading the manual fro one of those old push-button 1970s Flukes. Some of them have a 10 GOhm impedance mode for measuring voltage.

Up to 200 V? 10 GOhm up to 10 or 20 V is quite common in bench meters, but above that it is usually 10 MOhm.

[Alex Nikitin]

I was just reading the manual fro one of those old push-button 1970s Flukes. Some of them have a 10 GOhm impedance mode for measuring voltage.

Only on 0.2V and 2V ranges!

One can use something like this divider to achieve 1G input impedance for high voltages.

Cheers

Alex

[Fungus]

I was just reading the manual fro one of those old push-button 1970s Flukes. Some of them have a 10 GOhm impedance mode for measuring voltage.

Up to 200 V? 10 GOhm up to 10 or 20 V is quite common in bench meters, but above that it is usually 10 MOhm.

Nope.

I was just reading the manual fro one of those old push-button 1970s Flukes. Some of them have a 10 GOhm impedance mode for measuring voltage.

Only on 0.2V and 2V ranges!

Yep. The manual specifically mentions measuring voltages across the sense resistor of voltage dividers. 2V is enough to be useful for that.

[Fungus]

One can use something like this divider to achieve 1G input impedance for high voltages.

Making the divider is easy. Measuring it is hard.

[b_force]

There is one thing about trust though. With that I mean trust in your measurements.

I'd argue that owning two (or more) cheap meters gives more trust than a single expensive meter.

If you own a single meter how do you know it's working? You need at least a voltage/resistance/current reference apart from the meter.

What is important for me personally, is that the meter is sturdy enough.
I had some meters in the past, but the switch broke every time (of course in the most important moments), which was so frustrating.
For that reason I bought a very decent Brymen.

Owning 2+ cheap meters also solves that problem better than owning a single expensive meter.

I guess your trust levels are pretty low than?

I only had some strange issues with some old Fluke benchtop meters I had in the past (8010 & 8050, to bad I sold them)
But these meters were over 25-30 years old.

But yes, in general it's very handy to have an extra meter or some sort of voltage reference.
Although if your work is somewhat serious, you need a couple of meters anyway.

But I find the whole thing about trusting and proper meters and precision highly overlooked.
Especially calibrating. To me that's just pure marketing (unless you have to work on projects were extreme precision is needed)
Of course it depends on the type of work you're doing, but most circuits aren't so picky with the voltages.
So something like ±10% voltage difference is more than fine in many cases. Ballpark values are most of the time more than adequate. 
From a practical point of view even a $10 meter will be fine.
But like I said, these meter will mostly just (mechanically) brake pretty soon.
Especially when being used a lot.

[Fungus]

I would still argue that in regular use the chance of a cheap meter going wrong is higher than the root of the chance of an expensive meter going wrong (so both cheap meters may well die before the expensive meter dies).

No argument there, but... who cares when they're only $20 a pop?

I don't think owning a single meter is really possible so this argument is almost moot to me.

I simply fail to see how owning an expensive meter gives much more confidence or reliability than owning several cheaper ones. Check Dave's recent video on the AN8008. There's no reason to doubt the accuracy of even the cheapest meters.

Keep in mind that a more expensive meter will often have tighter specs, so while that 0.025% accurate meter could have drifted out of spec

I think drift is moot these days, too. Drift became a non-issue when they stopped using those crappy trimmer pots and switched to all-digital calibration.

You know the ones I mean...

[alm]

I simply fail to see how owning an expensive meter gives much more confidence or reliability than owning several cheaper ones. Check Dave's recent video on the AN8008. There's no reason to doubt the accuracy of even the cheapest meters.

Sure there is. There was a post about a brand new Uni-T meter being out of spec a couple of years ago. CAT ratings are not necessarily the only specification cheap manufacturers lie about. Most buyers would never be able to verify if their $20 meter is in spec. Evaluating accuracy and reliability requires much more than a single test of a single sample like Dave did. Results like I posted, based on multi-year performance of a couple of dozen meters, is how you gain confidence. Similar data is not available for cheap meters because a) they will most likely not be for sale for many years and b) few will ever see a cal lab, so how would you tell if it is still within specifications after a couple of years?

I think drift is moot these days, too. Drift became a non-issue when they stopped using those crappy trimmer pots and switched to all-digital calibration.

If you think that meters never drift significantly, then why would you need another meter to verify if they are still accurate? If a meter suddenly fails to power on, a fuse is open or it stops reading resistance, this is all trivial to test without external references.

[Fungus]

I guess your trust levels are pretty low than?

If it's a life and death measurement? I'll use two different meters and maybe check them against the voltage reference as well.

My trust level will be at least as good as yours.

[Fungus]

I simply fail to see how owning an expensive meter gives much more confidence or reliability than owning several cheaper ones. Check Dave's recent video on the AN8008. There's no reason to doubt the accuracy of even the cheapest meters.

Sure there is. There was a post about a brand new Uni-T meter being out of spec a couple of years ago.

You mean faulty meters exist? And it's a couple of years since you heard of one??

I'm sure I could point you to a Fluke or two that was out of spec when brand new(!). Wasn't there a thread a couple of weeks ago?

I think drift is moot these days, too. Drift became a non-issue when they stopped using those crappy trimmer pots and switched to all-digital calibration.

If you think that meters never drift significantly, then why would you need another meter to verify if they are still accurate?

Because 'drift' isn't the same as 'faulty'.

Because probe leads break.

etc.

I think the only broken meter I've owned is one that's about 20 years old and the 20V range is dodgy. You sometimes have to wiggle the selector switch for it to work on that range.

Maybe I could open it up and clean it and it work like like new. Maybe not.  I don't really care, I never liked that meter much anyway and my new ANENGs are in transit.

[kcbrown]

Would the Mooshimeter work?   https://moosh.im/mooshimeter/

No, because he requires 1GOhm impedance on voltage measurements.

Finding a 300V meter isn't difficult, it's the special requirements.

Hmm...just what sort of DUT impedances are we talking about here?

[Fungus]

Hmm...just what sort of DUT impedances are we talking about here?

To reiterate my needs:
1)Minimum of 4 channels
2)1 Gohm input impedance @ 200v (I often measure circuits with impedances between 10Mohm to 100Mohm)
3)300V+ range
4) (simple!) Data logging
5) I only need voltage readings, current and resistance measurements aren't required.

My wants:
Wall powered
Stackable

Even 1GOhm isn't much if your DUT is 100MOhm.

Maybe he could attach some pieces of tinfoil to the outputs and do some sort of non-contact capacitive measurement with an Arduino. 

[Alex Nikitin]

The Keithley 617 electrometer can measure up to 200V directly with a very high (over 200 Tohm) input impedance, and using the internal +/-100V voltage source as a reference this can be extended up to 300V.

Cheers

Alex

[Fungus]

The Keithley 617 electrometer can measure up to 200V directly with a very high (over 200 Tohm) input impedance

I think that might actually be higher impedance than the air between the input jacks.

[Alex Nikitin]

The Keithley 617 electrometer can measure up to 200V directly with a very high (over 200 Tohm) input impedance

I think that might actually be higher impedance than the air between the input jacks.

The K617 uses a triaxial connector with a guard ring, no input jacks as such. Nevertheless, the resistance between two properly isolated (PTFE) jacks would be much more than 1000 Tohm (for reasonable voltages, well below the air breakdown field strength, not in a presence of an ionization source, not very high humidity etc). The input impedance of that magnitude is measurable, if I connect (a properly screened) 1Tohm resistor in series with the input of the K617, the measured voltage (near full scale, say 190V) is changed by less than 0.25% of the value. On the other hand the K617 can measure resistances over 1000 Tohm on its own.

Cheers

Alex

[Eric_the_EE]

Just another example usage of expensive meters (at least for work, not necessarily hobbyist):
I recently used a Fluke 8846A precision bench meter to perform 4-wire resistance measurements while evaluating contact resistance change. The purpose of the experiment was to investigate galvanic corrosion effects on connector mating resistance. The measurement range I was looking at was in the 0.1 milliohm range. The Fluke has a statistics function which I used to take 1,000 samples and observe the min, max, and average measurements - much more reliable than me "eye-balling" the measurement myself.

[alm]

Should you not be using dry circuit testing when evaluating contact resistance to prevent sparks that may break through corrosion?

[Eric_the_EE]

I don't think this question is really related to the original thread, and I don't really want to create a rabbit hole, but I will respond because you raised a very interesting point. First, I wasn't performing compliance testing for connector manufacturing, or even cable harness assembly. I was performing a ball-park reality check when the mating connection was subjected to a very corrosive environment. Secondly, and most importantly, the connector I was testing will be used for 24V industrial I/O. The Fluke's 4-wire measurement spec is 13V, 5mA - much, much less power than the application circuit. So for my purpose, dry testing would have been overkill. But thank you for raising that interesting point that readers should keep in mind for smaller, low-power connectors, particularly important for compliance testing obviously.

[b_force]

I guess your trust levels are pretty low than?

If it's a life and death measurement? I'll use two different meters and maybe check them against the voltage reference as well.

My trust level will be at least as good as yours.

Well yeah, obviously.
The point is that these are not your average projects.

[G0MJW]

There is one thing about trust though. With that I mean trust in your measurements.

I'd argue that owning two (or more) cheap meters gives more trust than a single expensive meter.

If you own a single meter how do you know it's working? You need at least a voltage/resistance/current reference apart from the meter.

What is important for me personally, is that the meter is sturdy enough.
I had some meters in the past, but the switch broke every time (of course in the most important moments), which was so frustrating.
For that reason I bought a very decent Brymen.

Owning 2+ cheap meters also solves that problem better than owning a single expensive meter.

Reminds me of the old adage,

"A man with a watch knows what time it is. A man with two watches is never sure"

Having two meters reading differently leads to anxiety and hair loss.

Mike